Academic journal article Perception and Psychophysics

The Effect of Attentional Demands on the Antisaccade Cost

Academic journal article Perception and Psychophysics

The Effect of Attentional Demands on the Antisaccade Cost

Article excerpt

In the present study, we examined the effect of attentional demands on the antisaccade cost (the latency difference between antisaccades and prosaccades). Participants performed a visual search for a target digit and were required to execute a saccade toward (prosaccade) or away from (antisaccade) the target. The results of Experiment 1 revealed that the antisaccade cost was greater when the target was premasked (i.e., presented through the removal of line segments) than when it appeared as an onset. Furthermore, in premasked target conditions, the antisaccade cost was increased by the presentation of onset distractors. The results of Experiment 2 revealed that the antisaccade cost was greater in a difficult search task (a numeral 2 among 5s) than in an easy one (a 2 among 7s). The findings provide evidence that attentional demands increase the antisaccade cost. We propose that the attentional demands of the search task interfere with the attentional control required to select the antisaccade goal.

Human behavior can be characterized by its flexibility in responding to events in our environment. A classic demonstration of this flexibility was provided in a study by Hallett (1978; see also Hallett & Adams, 1980). Under normal circumstances, observers execute saccadic eye movements (saccades) toward objects that are of interest to their goals and desires. However, Hallett demonstrated that when observers were instructed to move their eyes in the opposite direction from a stimulus, they were able to execute such antisaccades on the vast majority of trials. In the original version of the task, participants were instructed to fixate a stimulus presented at the center of the screen. The stimulus abruptly stepped to the left or right of fixation, and participants were required to move their eyes in the direction opposite from the step (antisaccade). In another version of this antisaccade task (typically referred to as the overlap condition), there is no movement of a fixation stimulus, but a peripheral stimulus appears while the central fixation point remains on the screen. Participants were quite good at executing antisaccades, but on some trials they erroneously moved their eyes toward the stimulus (erroneous prosaccade), despite the instruction to move their eyes in the opposite direction.

Hallett and Adams (1980) developed a model of antisaccade generation in which a prosaccade program is automatically initiated. If the prosaccade program is completed before an antisaccade goal redefinition program is initiated, a prosaccade is executed. If the antisaccade goal redefinition process is initiated prior to the completion of the prosaccade program, that program is canceled, and an antisaccade is executed instead. Subsequently, Guitton, Buchtel, and Douglas (1985) found that patients with frontal-lobe damage executed a higher percentage of erroneous prosaccades in the antisaccade task than did a control group (see also Milea et al., 2003; Pierrot-Deseilligny, Ploner, Müri, Gaymard, & Rivaud-Péchoux, 2002; Pierrot-Deseilligny, Rivaud, Gaymard, & Agid, 1991; Walker, Husain, Hodgson, Harrison, & Kennard, 1998). Utilizing the Hallett and Adams model, they proposed that frontal-lobe damage delays the cancellation signal (or the goal redefinition process) such that, on many trials, it occurs too late to stop the execution of the prosaccade program.

Since these early studies, the antisaccade task has become one of the most popular eye movement paradigms. Its use has extended beyond behavioral and clinical studies, to developmental, human neuroimaging, and monkey neurophysiological studies (for a review, see Munoz & Everling, 2004). Given the popularity of the antisaccade task, as well as the ubiquitous nature of eye movements in most everyday behaviors, it is obvious that an understanding of the processes involved in antisaccade generation is of great importance.

Following the initial steps of Hallett and Adams (1980), more recent studies have further examined the processes involved in antisaccade generation (e. …

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